1. Field of the Invention
This invention relates to a vibration insulating mount, particularly to a vibration insulating mount which has a stopper device to prevent elastic deformation beyond its bounds upon an excessive external force.
2. Description of Related Art
A vibration insulating mount is shown in FIG. 9, which is an engine mount used for bearing the load of an engine of a vehicle.
FIG. 9 illustrates a section of the engine mount. As shown in the figure, the engine has a rubber body 11. A lower case 12 is fixed to a lower surface of the rubber body 11. The lower case 12 is made of a metal and formed into a cup shape that is opened upward. A lower attaching bolt 13 is projected downward from a lower surface of the lower case 12. A flanged body 14, has a lower flange 15 embedded in an upper part of the rubber body 11. The flanged body 14 protrudes upwardly from inside the rubber body 11. An upper attaching bolt 16 is projected upward from an upper surface of the flanged body 14. The lower case 12 and the flanged body 14 are formed into one body in a curing process of the rubber body 11.
A disc fitting plate 17 has a tapped hole 18 formed at its center and fitted on the upper attaching bolt 16 so as to be disposed upon the upper surface of the flanged body 14. A rubber ring 19 is cured and molded onto a lower surface of the fitting plate 17 about its circumference. A lower surface of the rubber ring 19 constitutes an upper support 20, while a troidal upper surface of the rubber body 11 constitutes a lower support 21. Both the supports 20 and 21 are opposed to each other by a fixed distance.
A cylindrical upper case 22 formed of a metal plate is arranged on an outer periphery of the rubber body 11. The upper case 22 has its entire lower end bent outwardly so as to enqage an outer periphery of the lower case 12. The outer periphery of the lower case 12 is caulked while covering the lower end of the upper case 22, so that both these cases 12 and 22 are made integral. An overall upper end of the upper case 22 is bent inwardly so as to define a circular clearance hole 24 at its center. An inner edge of the clearance hole 24 surrounds an outer peripheral surface of the flanged body 14 with a space therebetween. This upper bent section of the upper case 22 is used as a stopping section 23. The stopping section 23 is positioned between the upper support 20 and the lower support 21. As clearly shown in the figure, an inner diameter of the stopping section 23 is set smaller than an outer diameter of the upper and lower supports 20 and 21. Thus, the upper support 20 is struck on an upper surface of the stopping section 23, when the rubber body 11 is contracted. On the other hand, the lower support 21 is struck on a lower surface of the stopping section 23, when the rubber body is expanded.
Here, the stopping section 23 is not placed at a middle position between the supports 20 and 21, but is disposed at a position slightly lower than that, since a weighing down length of the rubber body 11 is taken into account, due to the weight of an engine. When the engine is put on the engine mount, the rubber body 11 is pressed so that the supports 20 and 21 move downward, thereby placing the stopping section 23 at a middle position.
As described above, the engine mount has a detachable fitting plate 17 provided on the flanged body 14. This is because, if the fitting plate 17 is fitted on the flanged body 14 before the upper case 22 is assembled on the lower case 12, the stopping section 23 interferes with the fitting plate 17, thereby making the assembly impossible. In order to remove such troubles, the engine mount adopts a structure such that the upper case 22 is assembled while the fitting plate 17 is detached.
Next, an operation of the above constructed engine mount is described. In an assembled state in a car, the engine mount has the lower attaching bolt 13 secured in an engine room of a car body (not shown). The upper attaching bolt 16 is fixed to a mounting bracket or the like of an engine block. Thus, the engine is supported on the car body via the engine mount. The fitting plate 17 is held and secured between the flanged body 14 and the mounting bracket or the like of the engine. When vibration is applied to the upper attaching bolt 16 in operating the engine, the vibration is transmitted from the upper attaching bolt 16 to the rubber body 11 via the flanged body 14. The rubber body 11 is thereby elastically deformed to dampen the vibration.
Moreover, in case a mechanical shock is applied to the car body in running the car, e.g. in off-road driving, or when a rapid change of a load on the engine takes place, the engine mount is exposed to internal forces much larger than forces of normal vibration of the engine. Then, in the engine mount, the rubber body 11 cannot be deformed enough to absorb the external force. For instance, when the external force is applied in a contracting direction, the rubber body 11 is contracted vertically, so that the upper support 20 is contacted with the upper surface of the stopping section 23. Subsequently, the rubber body 11 is prevented from further deformation, thereby avoiding breakage due to excessive contraction. When the external force is applied in an expanding direction, the rubber body 11 is expanded vertically, so that the lower support 21 is contacted with the lower surface of the stopping section 23. Subsequently, the rubber body 11 is prevented from breaking due to excessive expansion.
As mentioned above, the engine mount has the fitting plate 17 assembled as a separate member from the rubber body 11 and the flanged body 14. Thus, an extra manufacturing step for the fitting plate 17 is necessary, e.g. steps for molding the fitting plate 17, or curing and molding and coating adhesive on the rubber ring 19. This causes an increase of total manufacturing costs of the engine mount.
Moreover, the fitting plate 17 is detachably disposed on the engine mount and fixed just when the engine mount is set on the car body. Consequently, it is possible that the fitting plate 17 will drop out in the previous steps. Accordingly, manufacturing needs to be carried out while taking care of such possible drop-out, making the work troublesome.